Cancer Survivors Face Major Health Risks

Action Points

Explain that the summary report of a committee charged with examining radiotherapy-induced second malignancies and cardiovascular disease listed crucial research questions to address these downsides of successful cancer treatment.

Note that the report also included recommendations for awareness, evaluation, and counseling.

A growing population of cancer survivors faces an increased risk of radiation-related second malignancy and cardiovascular disease (CVD) for which little evidence-based clinical guidance has emerged, researchers found.

The number of cancer survivors in the U.S. has tripled since 1971. In that time, multiple epidemiologic studies have documented the health hazards associated with radiation therapy, but few studies have examined the consequences and outcomes among affected patients.

Moreover, accurate risk estimates have been complicated by use of risk-assessment models based on older technology that had different dose-distribution patterns compared with modern radiation therapy technology, according to a summary of scientific review findings published online in the Journal of the National Cancer Institute.

"For many survivors, the successes of treatment have been offset by the late effects of cancer and its therapy," Lois Travis, MD, of the University of Rochester in New York and first author of the report, said in a statement.

"Although many complex factors influence the risk of second malignancies and other health issues after cancer treatment ... it is vital that we develop the best possible long-term risk estimates and prediction models and that we establish research priorities and identify concrete ways to prevent serious additional health problems among cancer survivors."

The summary report provides an overview of findings from five years of study and discussion by a committee appointed by the National Council on Radiation Protection and Measurements (NCRP) to determine the state of knowledge about radiotherapy-induced cancers and cardiovascular disease.

As described in the summary, the NCRP committee examined several broad issues related to the secondary health effects of radiation therapy, including current understanding regarding radiobiology, the genetic underpinnings of radiotherapy's late effects, radiotherapy techniques and dosimetry, the epidemiology of secondary malignancies following radiation therapy in adults and in childhood, secondary malignancies and radiation dose-response relationships, and CVD after radiation therapy.

The research and discussion led to seven principal conclusions:

A growing number of cancer survivors are affected by radiation-induced second malignancies and CVD.

Quantitative estimates of radiation-induced second malignancies are based on older regimens but are still applicable to risk assessment in terms of organ-specific radiation doses and dose-response relationships.

Models developed for secondary malignancy risk assessment remain useful for older regimens, and similar models are needed for assessment of cardiovascular risk.

Low-dose radiation exposure in cardiac tissue has not been convincingly linked to CVD; whole-body dose assessments based on atomic bomb survivors may have relevance to low cardiac doses related to scatter and collimator leakage.

Few studies have examined survival among patients with radiation-induced second malignancies or CVD.

Risk assessment should not be based on effective dose but on organ-specific absorbed dose, biological effectiveness for the endpoint of interest, and radiation type.

The committee also cited general and specific needs for research into multiple aspects of the association between therapeutic radiation and secondary adverse health effects.

"Given the enormous strides that we have made in treating cancer, the scientific community is now shifting its thinking to how to best minimize the cost of the cure," Travis told MedPage Today in an email. "Additional research directed to not only quantifying the long-term risk but clarifying the mechanisms by which the late sequelae of cancer and its treatment develop are needed."

In focusing on the adverse health effects of radiotherapy, the scientific community and the public should "keep in mind that the benefits of both radiotherapy and chemotherapy for many cancers far outweigh the potential risks of serious adverse effects years later," she added.

The 425-page NCRP Scientific Committee 1-17 report will be available online later in the spring at http://www.ncrponline.org.

The study was supported by the National Institutes of Health, the American Lebanese Syrian Associated Charities, and the University of Rochester Medical Center.

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